What causes a P0138 code?

P0138 can be triggered by several issues — see the verified probable causes and step-by-step diagnostics shared by mechanics and owners on OBDIY.

Can I drive with a P0138 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with P0138 active.

Follow the step-by-step diagnostic on this page, then read the verified fixes contributed by other Heavy Truck owners — the answer marked "Verified Cause" worked for the original poster.

OBDIY

Log in Sign up

OBD-II

P0138

O2 Sensor Circuit High Voltage (B1S2)

What it means

High downstream signal

Sign in to view symptoms, probable causes, diagnostic steps, severity, and related codes

Log in Sign up free